1. Field of the Invention
The present invention relates to an oscillator used for communication of information of an electronic tag and in high-speed signal processing, for example.
2. Description of the Related Art
Microwaves are conventionally used for communication, heating, high-speed signal processing, and the like. In recent years, needs for a compact oscillator that transmits an electromagnetic wave have been increased in various applications. For example, it is expected that a compact oscillator having a size of 100 nm or less will be used for communication of information of an electronic tag or the like.
As an example of the compact oscillator which includes a ferromagnetic pinned layer whose magnetization direction is fixed, a nonmagnetic conductive layer, and a magnetic free layer whose magnetization direction is changeable stacked in that order is known (see, Japanese Patent Laid-Open Publication No. 2005-25831, for example). In this structure the magnetization direction of the free layer with low coercivity oscillates due to spin transfer effect (see, S. I. Kiselev et al., “microwave oscillations of a nanomagnet driven by a spin-polarized current”, Nature, Vol. 425, 380-383 (2003), for example).
However, it is difficult to adjust the oscillation frequency to a desired values in the aforementioned compact oscillator.